The goal of this Phase I SBIR project is to develop a scalable method of C2 purification for use in C2- replacement therapy based on a novel immunoaffinity chromatography resin. Deficiency of complement C2 (C2D) is reported to be the most common hereditary defect among complement components with a prevalence of 1: 20,000. Patients with homozygous complete deficiency suffer from recurring pyrogenic infections with encapsulated bacteria. C2 deficiency is also thought to cause a defect in the clearance of immune complexes and lead to auto-immune disease. An estimated 10 to 30% of individuals with a C2 deficiency eventually develop a form of systemic lupus erythematosous (SLE). Despite the unmet medical need, no therapies for C2D are known to be under development. Preclinical and clinical evidence supports enzyme replacement therapy as a promising approach for treating C2D. Addition of recombinant or plasma-derived C2 restores the function of classical and lectin pathways in ex vivo assays with serum either obtained from normal patients and depleted by immunoaffinity chromatography or obtained from C2D patients. If all symptomatic patients in the U.S. were to be treated with C2 replacement, the annual requirement of drug substance would be approximately 5 kg per year, well within the range of feasibility expected for modern biologics manufacturing. However, a major obstacle to the development of C2 replacement therapy is the lack of a scalable method for purifying C2. To date, reported purification methods are inadequate to produce C2 at the scale and purity necessary to make replacement therapy a viable option. nanoCLAMPs are a newly described class of single domain affinity reagents with high affinity, high specificity and the rare property of polyol-responsiveness. Functionally and structurally intact targets can be released from nanoCLAMP affinity resins upon exposure to buffer containing polyol and salt. Panels of nanoCLAMPs to new protein targets are easily generated from our validated synthetic phage display library, and the high-binding capacity affinity resins generated from them yield highly pure, active target proteins free of column leachate. We propose to isolate and rank a set of high performing anti-C2 nanoCLAMPs useful for single-step purification of C2 and assess their binding capacity, selectivity and yield in small scale purifications of C2 from human serum. We will identify candidates with the ability to produce C2 with high yield and purity and free from contamination with C2a and C2b. We will then test the activity of the purified C2 in functional assays to validate the approach, and finally develop an optimize, scaled up procedure for purifying C2 on a kg scale. We will use these measurements to project the method?s potential to support economically viable purification at the kg scale required to treat a significant fraction of the patient population.